what is visual state in wpf? and anyone knows how to start understand and use that?
maybe like a complete tutorial, because i never touch visual state before. or just a simple example code
Visual States in WPF are about controlling the appearance of controls. It is possible for the state of a control to change then have the appearance of the control change in response to the state change. For example if a control is pressed/disabled/in focus it may have a different appearance for each state. There is an example of how to use WPF's trigger mechanism to change the appearance of controls here; that will provide you with some general background information on changing the appearance of controls. There are nice general tutorials on WPF here and here. For more advanced use there is information on the Visual State Manager here